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[209.132.180.67]) by mx.google.com with ESMTP id y9-v6si5150262plk.427.2018.08.24.00.56.25; Fri, 24 Aug 2018 00:56:41 -0700 (PDT) Received-SPF: pass (google.com: best guess record for domain of linux-kernel-owner@vger.kernel.org designates 209.132.180.67 as permitted sender) client-ip=209.132.180.67; Authentication-Results: mx.google.com; spf=pass (google.com: best guess record for domain of linux-kernel-owner@vger.kernel.org designates 209.132.180.67 as permitted sender) smtp.mailfrom=linux-kernel-owner@vger.kernel.org Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1727650AbeHXL2r (ORCPT + 99 others); Fri, 24 Aug 2018 07:28:47 -0400 Received: from terminus.zytor.com ([198.137.202.136]:37539 "EHLO terminus.zytor.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726969AbeHXL2q (ORCPT ); Fri, 24 Aug 2018 07:28:46 -0400 Received: from terminus.zytor.com (localhost [127.0.0.1]) by terminus.zytor.com (8.15.2/8.15.2) with ESMTPS id w7O7t1Ao3564674 (version=TLSv1.2 cipher=ECDHE-RSA-AES256-GCM-SHA384 bits=256 verify=NO); Fri, 24 Aug 2018 00:55:01 -0700 Received: (from tipbot@localhost) by terminus.zytor.com (8.15.2/8.15.2/Submit) id w7O7t0Ar3564671; Fri, 24 Aug 2018 00:55:00 -0700 Date: Fri, 24 Aug 2018 00:55:00 -0700 X-Authentication-Warning: terminus.zytor.com: tipbot set sender to tipbot@zytor.com using -f From: tip-bot for Vlastimil Babka Message-ID: Cc: mhocko@kernel.org, torvalds@linux-foundation.org, studio@anchev.net, ak@linux.intel.com, dave.hansen@intel.com, kode54@gmail.com, linux-kernel@vger.kernel.org, hpa@zytor.com, vbabka@suse.cz, mingo@kernel.org, tglx@linutronix.de Reply-To: kode54@gmail.com, linux-kernel@vger.kernel.org, hpa@zytor.com, vbabka@suse.cz, mingo@kernel.org, tglx@linutronix.de, mhocko@kernel.org, torvalds@linux-foundation.org, studio@anchev.net, ak@linux.intel.com, dave.hansen@intel.com In-Reply-To: <20180823134418.17008-1-vbabka@suse.cz> References: <20180823134418.17008-1-vbabka@suse.cz> To: linux-tip-commits@vger.kernel.org Subject: [tip:x86/urgent] x86/speculation/l1tf: Fix off-by-one error when warning that system has too much RAM Git-Commit-ID: b0a182f875689647b014bc01d36b340217792852 X-Mailer: tip-git-log-daemon Robot-ID: Robot-Unsubscribe: Contact to get blacklisted from these emails MIME-Version: 1.0 Content-Transfer-Encoding: 8bit Content-Type: text/plain; charset=UTF-8 Content-Disposition: inline X-Spam-Status: No, score=-0.5 required=5.0 tests=ALL_TRUSTED,BAYES_00, FREEMAIL_FORGED_REPLYTO,FREEMAIL_REPLYTO_END_DIGIT,T_DATE_IN_FUTURE_96_Q autolearn=no autolearn_force=no version=3.4.1 X-Spam-Checker-Version: SpamAssassin 3.4.1 (2015-04-28) on terminus.zytor.com Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Commit-ID: b0a182f875689647b014bc01d36b340217792852 Gitweb: https://git.kernel.org/tip/b0a182f875689647b014bc01d36b340217792852 Author: Vlastimil Babka AuthorDate: Thu, 23 Aug 2018 15:44:18 +0200 Committer: Thomas Gleixner CommitDate: Fri, 24 Aug 2018 09:51:14 +0200 x86/speculation/l1tf: Fix off-by-one error when warning that system has too much RAM Two users have reported [1] that they have an "extremely unlikely" system with more than MAX_PA/2 memory and L1TF mitigation is not effective. In fact it's a CPU with 36bits phys limit (64GB) and 32GB memory, but due to holes in the e820 map, the main region is almost 500MB over the 32GB limit: [ 0.000000] BIOS-e820: [mem 0x0000000100000000-0x000000081effffff] usable Suggestions to use 'mem=32G' to enable the L1TF mitigation while losing the 500MB revealed, that there's an off-by-one error in the check in l1tf_select_mitigation(). l1tf_pfn_limit() returns the last usable pfn (inclusive) and the range check in the mitigation path does not take this into account. Instead of amending the range check, make l1tf_pfn_limit() return the first PFN which is over the limit which is less error prone. Adjust the other users accordingly. [1] https://bugzilla.suse.com/show_bug.cgi?id=1105536 Fixes: 17dbca119312 ("x86/speculation/l1tf: Add sysfs reporting for l1tf") Reported-by: George Anchev Reported-by: Christopher Snowhill Signed-off-by: Vlastimil Babka Signed-off-by: Thomas Gleixner Cc: "H . Peter Anvin" Cc: Linus Torvalds Cc: Andi Kleen Cc: Dave Hansen Cc: Michal Hocko Cc: stable@vger.kernel.org Link: https://lkml.kernel.org/r/20180823134418.17008-1-vbabka@suse.cz --- arch/x86/include/asm/processor.h | 2 +- arch/x86/mm/init.c | 2 +- arch/x86/mm/mmap.c | 2 +- 3 files changed, 3 insertions(+), 3 deletions(-) diff --git a/arch/x86/include/asm/processor.h b/arch/x86/include/asm/processor.h index a0a52274cb4a..c24297268ebc 100644 --- a/arch/x86/include/asm/processor.h +++ b/arch/x86/include/asm/processor.h @@ -183,7 +183,7 @@ extern void cpu_detect(struct cpuinfo_x86 *c); static inline unsigned long long l1tf_pfn_limit(void) { - return BIT_ULL(boot_cpu_data.x86_phys_bits - 1 - PAGE_SHIFT) - 1; + return BIT_ULL(boot_cpu_data.x86_phys_bits - 1 - PAGE_SHIFT); } extern void early_cpu_init(void); diff --git a/arch/x86/mm/init.c b/arch/x86/mm/init.c index 02de3d6065c4..63a6f9fcaf20 100644 --- a/arch/x86/mm/init.c +++ b/arch/x86/mm/init.c @@ -923,7 +923,7 @@ unsigned long max_swapfile_size(void) if (boot_cpu_has_bug(X86_BUG_L1TF)) { /* Limit the swap file size to MAX_PA/2 for L1TF workaround */ - unsigned long long l1tf_limit = l1tf_pfn_limit() + 1; + unsigned long long l1tf_limit = l1tf_pfn_limit(); /* * We encode swap offsets also with 3 bits below those for pfn * which makes the usable limit higher. diff --git a/arch/x86/mm/mmap.c b/arch/x86/mm/mmap.c index f40ab8185d94..1e95d57760cf 100644 --- a/arch/x86/mm/mmap.c +++ b/arch/x86/mm/mmap.c @@ -257,7 +257,7 @@ bool pfn_modify_allowed(unsigned long pfn, pgprot_t prot) /* If it's real memory always allow */ if (pfn_valid(pfn)) return true; - if (pfn > l1tf_pfn_limit() && !capable(CAP_SYS_ADMIN)) + if (pfn >= l1tf_pfn_limit() && !capable(CAP_SYS_ADMIN)) return false; return true; }